As is known, from the reaction between oxygen and tetrafluoroethylene conducted at low temperature, in the presence of U.V. radiations and in an inert solvent, generally a perfluorocarbon or a fluorochlorocarbon, a perfluoropolyether is obtained, which exhibits a peroxidic oxygen content varying as a function of the operative conditions under which the photo-oxidation has been conducted. Such content, expressed as % by weight, corresponds to a gram-atom of oxygen for each peroxy-group. Generally, the oxygen peroxide content ranges from 0.7 to 2.8% by weight. The conversion of such product to perfluoropolyether free from peroxidic oxygen if carried out merely by heat treatment, leads to a final product whose molecular weight is too high for most of the applications known so far.
As it is known, peroxidic oxygen can be removed from the peroxidized precursors also by reduction with proper reducing agents: in such case the perfluoropolyether chain breaks in positions corresponding to peroxy-bond --O--O--. In such manner it is possible to obtain products exhibiting also a rather low molecular weight. However, instead of the oxygen peroxide it is possible to introduce also functional groups deriving from the reducing substance employed; furthermore it often happens that the molecular weight cannot be well adjusted.